Vinyl chloride resin (PVC) exhibits excellent moldability, can be provided with a variety of colors, and can be formed into products with various designs. In addition, PVC exhibits excellent properties (e.g., sheet moldability, installation performance, chemical resistance, and antifouling property). Therefore, PVC floor tiles have been widely used in place of, for example, conventional linoleum tiles or stone tiles.
However, PVC floor tiles generate toxic chlorine gas in the event of a fire. Therefore, attempts have been made to develop a non-vinyl chloride floor tile which does not generate chlorine gas. In recent years, attempts have also been made to develop a floor tile which does not contain a plasticizer (e.g., a phthalic acid ester)—such a plasticizer has been used in soft PVC materials and has been considered to be endocrine disruptors. Thus, demand has arisen for development of an environmentally friendly material.
Hitherto, there have been many proposals to meet the aforementioned demand. For example, there has been proposed a composition containing no halogen atom; i.e., a composition containing a filler and an olefin resin having a polar group, an ethylene-vinyl acetate copolymer (EVA), an ethylene-ethyl acrylate copolymer (EEA), an ethylene-methyl acrylate copolymer (EMA), or an ethylene-methyl methacrylate copolymer (EMMA). However, in view that, for example, the composition is molded into a sheet only within a narrow temperature range, and a sheet molded therefrom within such a temperature range exhibits low strength, the composition is not satisfactory as an alternative to a resin composition for PVC floor tiles. Meanwhile, conventional non-vinyl chloride floor tiles are inferior to PVC floor tiles, in terms of dimensional stability, adhesion-to-wax property, and bonding-to-base property.
Conventional PVC floor tiles or non-vinyl chloride floor tiles have a drawback in that they exhibit very high temperature sensitivity (i.e., large temperature-dependent change in flexibility), and thus the formulation of a resin composition for forming such tiles must be varied according to the season. Therefore, demand has arisen for development of a resin composition for non-vinyl chloride floor tiles, the composition having sheet moldability comparable or superior to that of a conventional resin composition for PVC floor tiles, as well as development of a non-vinyl chloride floor tile which exhibits excellent scratch resistance, dimensional stability, bonding-to-base property, installation performance, and flexibility, and which is satisfactory as an alternative to a PVC floor tile.
Under such circumstances, for example, Patent Document 1 discloses a polyolefin flooring material containing a polyolefin (A) having high stereoregularity in which the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn); i.e., (Mw/Mn), falls within a range of 1.2 to 4, and Mn is 10,000 to 2,000,000; a polar resin (B) having compatibility with the polyolefin (A); and, optionally, a filler (C) such as calcium carbonate, talc, or silica, wherein the amounts of the polyolefin (A), the polar resin (B), and the filler (C) are 100 parts by weight, 10 to 50 parts by weight, and 500 parts by weight or less, respectively. Patent Document 2 discloses a flooring material consisting of a polyolefin resin composition, the composition containing a C4-C8 α-olefin-ethylene copolymer (A) having a melting peak Tm at 90 to 110° C. as determined through heat flow differential scanning calorimetry (DSC); a propylene resin (B) having a melting peak Tm at 120 to 140° C. as determined in a manner similar to that described above; a petroleum resin (C) having a softening point of 90 to 150° C.; and optionally, an additive such as a filler. However, these flooring materials are inferior to the aforementioned PVC floor tiles (in terms of scratch resistance and bonding-to-base property) or resin compositions therefor (in terms of sheet moldability). In addition, these flooring materials require improvement of impact resistance.
Patent Document 3 discloses a floor tile formed from a composition containing a thermoplastic polymer component (100 parts by weight) and a filler (900 parts by weight or less), wherein the polymer component contains a specific amount of a block copolymer and/or a hydrogenated product thereof (A), the block copolymer having at least one polymer block formed mainly of a vinyl aromatic compound, and at least one polymer block formed mainly of a conjugated diene compound; a specific amount of a polyolefin resin (B); a specific amount of a polar-group-having ethylene copolymer (C); and optionally, a specific amount of a tackifier (D), a PTFE resin (E), or an acrylic resin (F). This flooring material exhibits, for example, improved moldability, shape-changing property (relaxation of upthrust stress by tile elongation), scratch resistance, and bonding-to-base property, as compared with a resin composition used for conventional non-vinyl chloride floor tiles or flooring materials (see, for example, Patent Document 1 or 2). However, this flooring material is inferior to such a resin composition in terms of dimensional stability and requires improvement of impact resistance and temperature sensitivity (difference between sheet flexibility in summer and that in winter).    Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. H09-32258.    Patent Document 2: Japanese Patent Application Laid-Open (kokai) No. 2000-53822.    Patent Document 3: Japanese Patent Application Laid-Open (kokai) No. 2003-327844.